包含不能翻译 EF .net 核心 3.1

Question

Hello I try to make a query on EF 3.1 like this:

  Expression<Func<MedicalResponsibleWard, bool>> predicate = x => x.InstitutionId == request.InstitutionId;
        if (request.GroupId != null)
            predicate = predicate.AndAlso(x => x.GroupId == request.GroupId);
        if (request.Code != null)
            predicate = predicate.AndAlso(x => x.Code == request.Code);
       
            if (request.MedicalResponsibleWarName != null)
                predicate = predicate.AndAlso(x => x.Properties.Any(m => m.Name.Contains(request.MedicalResponsibleWarName, StringComparison.InvariantCultureIgnoreCase)));

        return (await _genericRepository.GetAsync(predicate, query => query.Include(c => c.Properties)))
         .OrderBy(g => g.Id).ToList();

But the transaltion fail because this predicate

if (request.MedicalResponsibleWarName != null)
            predicate = predicate.AndAlso(x => x.Properties.Any(m => m.Name.Contains(request.MedicalResponsibleWarName, StringComparison.InvariantCultureIgnoreCase)));

And the error is

The LINQ expression 'DbSet<MedicalResponsibleWardProperty>
.Where(m0 => EF.Property<Nullable<int>>((EntityShaperExpression: 
    EntityType: MedicalResponsibleWard
    ValueBufferExpression: 
        (ProjectionBindingExpression: EmptyProjectionMember)
    IsNullable: False
), "Id") != null && EF.Property<Nullable<int>>((EntityShaperExpression: 
    EntityType: MedicalResponsibleWard
    ValueBufferExpression: 
        (ProjectionBindingExpression: EmptyProjectionMember)
    IsNullable: False
), "Id") == EF.Property<Nullable<int>>(m0, "MedicalResponsibleWardId"))
.Any(m0 => m0.Name.Contains(
    value: __request_MedicalResponsibleWarName_1, 
    comparisonType: InvariantCultureIgnoreCase))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync(). See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

How can fix it please? Regards

Answer 1

Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync()

The problem is mentioned in the explanation, this kind of queries requires client side evaluation, which is off by default. This type of evaluation is not supported on server side because it needs to load the entities into the memory and filter a large amount of data and that could result in bad performance. For more details see Unsupported client evaluation .

Actually, I went through this problem and found a better approach using a third party nuget as suggested by Microsoft docs . Download and install LinqKit , then you can use the dynamic composing expression predicates :

IQueryable<Product> SearchProducts (params string[] keywords)
{
  var predicate = PredicateBuilder.False<Product>();

  foreach (string keyword in keywords)
    predicate = predicate.Or (p => p.Description.Contains (keyword));

  return dataContext.Products.Where (predicate);
}